Triiodide in zeolites with catalytic, electronic, antiseptic and clinical applications

Abstract

The present invention describes a method for synthesising triiodide anions inside zeolites in a single reactor by means of a cascade reaction comprising dehydroiodination of alkyl iodides and oxidation in-situ with air, generating a solid material that can be used as a heterogeneous catalyst, an electrolyte for photovoltaic or perovskite cells and an agent for controlled release of triiodide for disinfection and hypothyroidism.

Description

[0001] DESCRIPTION

[0002] TRIIODIDE IN ZEOLITES WITH CATALYTIC, ELECTRONIC, ANTISEPTIC AND CLINICAL APPLICATIONS

[0003] Field of invention

[0004] The present invention describes a process for the synthesis of triiodide anions inside zeolites in a single reactor, by means of a cascade reaction of dehydroiodination of alkyl iodides and in-situ oxidation with air, such that the zeolite fills its pores with high amounts of triiodide anion and generates a solid material with application as a heterogeneous catalyst, electrolyte for photovoltaic cells or perovskites, and a controlled release agent of triiodide for disinfection of surfaces, water, or skin infections, as well as a supplier of iodine for hypothyroidism.

[0005] Background

[0006] The triiodide anion is widely recognized as the stable species for storing diiodine. In mixtures with the iodide anion, these compounds have universal applications in certain industrial catalytic processes and in the construction of photovoltaic cells, where it acts as an electrolyte. Furthermore, diiodine is recognized by the World Health Organization (WHO) as an essential medicine for the treatment of waterborne and human and animal infections due to its high antimicrobial capacity. Therefore, the triiodide anion is widely used in various industrial fields, even though it is administered by solution, as stable preparations in pure solid form are not known.

[0007] The most common form of synthesis, storage, and administration of the triiodide anion, and therefore of diiodine and iodide, is as a polymer in alcoholic solution, known by its generic names as povidone-iodine or iodine tincture, or by its trade name Betadine (R)This polymer is composed of polyvinylpyrrolidone containing adsorbed triiodide species, which have been added by sublimation of iodine onto the polymer. The synthetic process is inefficient in incorporating and utilizing iodine, and the resulting material contains at most 10% iodine by weight (in the form of triiodide), of which only 1% can be applied clinically, because the instantaneous release of all the iodine contained in the polymer can be harmful (Rev. J. Chem., 2020, 10, 40-57). In fact, it is considered that only a very small percentage of the instantaneously released triiodide evolves into active iodine. Therefore, this material is not viable for controlled release and does not allow the preparation of materials with a higher iodine load due to the low efficiency of the current synthetic process.The direct sublimation synthesis of iodine relies on the well-known ability of certain polymers to coordinate iodine or triiodide within their polymer chains. This is the basis for the classic analytical determination of iodine in starchy water, which produces an intense blue color (Angew. Chem. Int. Ed. 2016, 55, 8032-8035), always in solution and at low iodine concentrations. Therefore, new synthetic processes for triiodide-containing materials are needed, ideally through reactions other than the inefficient and aggressive direct sublimation of diiodine. Furthermore, these new triiodide-containing materials should ideally be insoluble solids to achieve a higher weight-to-iodine content ratio, improved storage and transport, and better controlled release.

[0008] Zeolites are crystalline microporous aluminosilicates with a high internal surface area (greater than 500 square meters per gram), widely used in everyday life as laundry detergent, pet litter, and so on, and particularly as catalysts for petrochemical processes. In fact, zeolites are considered the most produced catalytic materials by annual volume worldwide. Therefore, these microporous materials, harmless to human health, are ideal for housing species within them and releasing them in a controlled manner. However, zeolites are known for exchanging cations, not anions (in fact, their function as laundry detergent is to soften wash water by exchanging calcium cations for sodium ions), so it is difficult to imagine that anions of any kind, and especially triiodide anions with a considerable ionic radius, could be housed inside zeolites.Consequently, it is difficult to find halogenated zeolites in the literature, and only a few precedents describe the inclusion of triiodide anions in zeolites, but all of them by adsorption of iodine + iodide, and not by in-situ generation from alkyl iodides.

[0009] One document (Catal. Sci. Technol. 2023, 13, 2308-2316) shows that anion exchange can occur within the zeolite, but with halogen groups and not with th- or poly-anions. Another document (J. Phys. Chem. B 1999, 103, 6277-6282) reports a study on the basicity of zeolites X and Y exchanged with alkali metals (Na, K, Cs), using iodine adsorption and analysis by diffuse reflectance spectroscopy techniques. In this study, iodine adsorption tests were performed on a series of zeolites, including NaX and NaY, by exposing the sample in a quartz tube under pressure and at high temperature to iodine vapor. Spectroscopic analyses performed demonstrate the possible formation of a cesium triiodide salt in zeolites containing occluded cesium oxide, CsY and CsOx / CsY, due to the adsorption of iodine, which reacts irreversibly with the occluded alkaline species.The formation of the triiodide ion is only possible if molecular iodine dissociates first, which requires the presence of strongly basic sites on the zeolites, where it becomes adsorbed. As a complement to the adsorption studies, the activity of the zeolites with alkali metals was investigated in base-catalyzed reactions for the formation of ethylene carbonate from ethylene oxide and carbon dioxide.

[0010] Another document (Micropor. Mesopor. Mater. 2007, 99, 244-250) also discloses the adsorption of iodine in zeolites as a tool to analyze the modifications that take place on the inner surface of a zeolite A (LTA typology) by exchange of the compensating cations and that are not part of the structural framework (L1). + , Na + , K + , Rb + and Cs +The techniques used to determine the geometric, electronic, and vibrational structure of molecular iodine show that the molecules embedded in the inner surface of the zeolite are strongly influenced by the electric fields generated by the cations present, modifying the average bond distances and the electronic structure. As in the previous document, iodine insertion is performed by subjecting dehydrated zeolites to iodine in a quartz tube, using a separate container for the crystalline iodine.

[0011] In zeolites exchanged with Rb and Cs, with strongly basic properties, triiodide ions are apparently formed.

[0012] Regarding the reactivity of alkyl iodides within zeolites and, where applicable, the formation of alkenes, a document (Micropor. Mesopor. Mater. 2008, 108, 103-111) presents a study on nucleophilic substitution and elimination reactions of alkyl halides carried out in Faujasite NaX-type zeolites, and their dependence on the nature of the halogen, the type of halogenated carbon, and the chain length. To this end, a series of primary, secondary, and tertiary alkyl halides (chlorides, bromides, and iodides) were adsorbed onto a NaX zeolite at room temperature, and the resulting products were subsequently analyzed by NMR. 13 C and 1H and IR. Unlike primary alkyl chlorides and bromides, which underwent dehalogenation and dehydrohalogenation reactions, forming alkoxylated and definite species, respectively, primary alkyl iodides only yielded alkoxylated zeolitic structures. Secondary iodoalkanes gave both products, while secondary chlorine and bromoalkanes mainly yielded definite. Tertiary halides were all inactive. Ethyl halides did not form definite, which were obtained from longer-chain alkyl halides.The equilibrium between substitution and elimination can be understood based on two factors: the relative rates of CX (X = Cl, Br, I) and C-H bond cleavage, with substitution predominating when the CX bond cleavage rate is greater than that of the C-H bond; and the relative stability of the resulting alkoxylated structures, which decreases in the order I > Br > Cl, a result of spherical hindrance in the zeolite. The results obtained in tests performed with iodoalkane vapors show that the adsorption of ethyl iodide onto a NaX zeolite caused ethoxylation of the structure, while the reaction of 1-iodopropane, 1-iodobutane, and 1-iodopentane led only to alkoxylated structures (propoxylated, butoxylated, and pentoxylated, respectively). However, secondary alkyl iodides yielded the corresponding alkenes.Thus, 2-iodopropane and 2-iodobutane resulted in mixtures in which the main component was the alkene, propene and 2-butene, respectively.

[0013] Similarly, the document (Micropor. Mesopor. Mater. 2006, 92, 292-299) presents a study on the chemistry of alkyl halides in zeolites treated with Na°, concluding that untreated zeolites exhibit nucleophilic reactions due to the electron-donating nature of the host, while zeolites treated with Na° display nucleophilic, electron-transfer, and free-radical reactions. Within this study, faujasite-type zeolites NaX and NaY and their Na°-treated forms were exposed to linear 1-haloalkanes. The NaY zeolites proved inert, while in the NaY zeolites, by treatment with bromo- and iodoalkanes, alkoxylated structures and halide ion were formed, due to the electrophilic attack of the oxygen of the zeolitic framework on the alkyl halide, while the exit of the halide ion is assisted by the electrostatic attraction of the Na ions present.In NaX or NaY zeolites treated with Na. 0 , the direct reaction of Na 0 with an alkyl bromide or aldehyde yields a larger alkane and a halide ion, probably due to a free radical mechanism involving two Na 0and two molecules of alkyl halide. The reaction between the zeolite NaX and an alkyl chloride causes dehydrohalogenation, yielding 1-alkenes and chloride ions. In the case of the zeolites Na° / NaX and Na° / NaY, in the presence of alkyl chlorides, the dehydrohalogenation reaction produces chloride ions and 2-alkenes in low yields and alkanes in higher yields. Among the haloalkanes tested are methyl iodide, ethyl iodide, and 2-iodobutane. The adsorption of methyl iodide onto NaX, Na / NaX, NaY and Na / NaY zeolites resulted in species with methoxyl groups in the zeolitic framework, also obtaining ethane in the case of Na / NaX and Na / NaY, generating iodide ion but not triiodide in all cases.A similar result was obtained in the adsorption experiments of ethyl iodide and 1-iodobutane on these zeolites, observing the formation of ethoxylated and butoxylated species, in addition to longer alkanes, such as butane, detected in the tests with ethyl iodide. This document also describes the tests carried out to determine the amount of iodide generated by exposure of Na° / NaX, Na° / NaY, NaX, and NaY zeolites to methyl iodide.

[0014] There are precedents regarding the generation of triiodide ions within other porous solid systems. For example, a recent paper (J. Phys. Chem. C 2023, 127, 4618-4635) describes materials belonging to the UiO family of metal-organic frameworks (MOFs) derived from 2-amino-[1,T-biphenyl]-4,4'-dicarboxylic acid, with a high capacity for the adsorption of molecular iodine and its transformation into triiodide anions within the porous system. Specifically, three UiO-67_NH2 samples with different metal contents (Zr, Zr / Hf, and Hf) were used. After being exposed to I2 vapor for 48 hours at room temperature, they were subjected to Raman spectroscopy.In this way, the species present (I2 and I3-) and their spatial distribution along the crystals of the materials were evaluated, which correlates with the diffusion process of both, thus improving the understanding of the mechanism responsible for the conversion of iodine and its stabilization in UiO-type materials. The reduction of molecular iodine (I2) to triiodide ion is attributed to a donor-acceptor complex (EDA) formed between molecular iodine and the aromatic ring of the UiO structure's spacer, which is favored by the presence of a strongly electron-donating amino group (NH2) in the MOF's organic molecule.

[0015] Another recent example involves the use of a metal-organic framework (MOF) to incorporate triiodides into its structure and release them after applying infrared light to gold nanoparticles previously inserted within it (Adv. Funct. Mater. 2022, 32, 2112902). However, this material is expensive and is manufactured by iodine sublimation (Electrochimica Acta 2020, 337, 135825), similar to povidone or iodine tincture, which is much less effective than the methodology described in the present invention.

[0016] In this patent, we describe the in situ generation of triiodide anion within zeolites by means of a dehydrohalogenation reaction of alkyl iodides to gaseous alkenes and iodide anions, and subsequent in-situ oxidation with air, all in a single step, as shown in Figure 1.

[0017] The first electroneutral reaction allows the introduction of anions through the dehydrohalogenation of neutral organic molecules. This occurs exclusively within the zeolite, generating iodide in the pores and allowing atmospheric oxygen to diffuse in and oxidize the iodide to triiodide. This second reaction is only efficient due to the high concentration of iodides inside the zeolite, which allows the oxidation of these iodides to occur in air without requiring stronger external oxidizing agents. Furthermore, this effect is achieved solely by utilizing the zeolite's large internal surface area and its molecular-sized cavities. In this way, an exceptionally high quantity of triiodide supported on a solid material is generated—up to 50% by weight of the recovered catalyst—far exceeding any known triiodide-supported material.The zeolite is so packed with triiodide (electrically compensated by the exchange cations of the zeolite lattice) that the solid aluminosilicate is difficult to disaggregate in hydrofluoric acid (J. Am. Chem. Soc. 2000, 122, 4345-4351), unlike any conventional zeolite (Mater. Today Proceed. 2022, 55 46-51). It is worth noting that the starting alkyl iodide is an inexpensive organic compound, similar in price to diiodide, and that it can be regenerated after its use in the preparation of the material, since the resulting gaseous alkene (which is the only byproduct of the preparation reaction) can be regenerated to the starting iodide by treatment with hydriodic acid (Tetrahedron Lett. 2018, 59, 4293-4298; Tetrahedron 2019, 75, 3510-3515).The synthesis of the material occurs without any additional or intermediate substances (oxidation with air produces water, which evaporates), and no solvents are used, making the synthesis completely atomically and economically efficient. The only byproducts generated, gaseous alkenes and water, are recovered as gas and can be reused in a separate reactor (Org. Lett. 2000, 2, 369-372). The starting weight to final weight ratio is very similar, and the material preparation has a weight-to-weight yield greater than 80%. It can be easily scaled up to multi-kilogram levels without requiring large reactor volumes, with a volume efficiency also greater than 80%.

[0018] The microporous structure of the zeolite allows the triiodides thus formed to be protected within the material, as in perovskites (Science 2018, 361, 151-155), preventing their volatilization or degradation, and enabling the controlled release of these anions through passive diffusion or with external stimuli (light, electricity, etc.). The material can remain extremely charged with triiodides at room temperature and without any special protection for months, since the release is controlled and not immediate, resulting in a solid material with high effectiveness per weight, unlike other materials available on the market.The synthesis of the material described here is conceptually original and cannot be inferred from any previous preparation method, including materials supported on zeolites. Therefore, this new material has a high capacity for innovation in the various fields where it is applied, which are any fields where the triiodide anion is commonly used. Among these, we highlight the catalytic activity that the new material can provide in industrial reactions (Iodine Catalysis in Organic Synthesis, 2022, WILEY-VCH GmbH), such as the synthesis of formic acid from methanol after carboxylation (Chin. J. Catal. 2024, 56, 122-129), or the isomerization of fatty acids from biomass, among others (J. Am. Chem. Soc. 2021, 143, 19262-19267), which are currently carried out industrially using iodide or diode anions.In the field of photovoltaic cells (Science Advances 2022, 8(25), eabo1621), the new material provides a solid electrolyte for fully solid-state cells (Sol. St. Ion. 1993, 66, 189-194), unlike the current liquid iodide-triiodide electrolyte, which requires preparing photovoltaic cells by physically confining the liquid electrolyte between fused metal plates. Furthermore, it can complement photovoltaic-capable perovskites (ACS Appl. Mater. Interf. 2023, 15, 52661-52672), since these perovskites necessarily contain triiodides. In the field of antisepsis, the new material allows the controlled release of iodine, for example, in water for drinking water, unlike the current material which must be completely dissolved (Wildern. Environm. Med. 2010, 21, 332-336).The new material would also have applications in controlled release on solid surfaces, unlike current soluble materials which are not suitable. This would allow for prolonged disinfection of doorknobs, tabletops, and other surfaces, with particular interest in the hospital setting, thus replacing current materials based on either silver or antibiotics, which are much more expensive. Finally, microporous zeolites with triiodide would provide a material of great interest in the clinical field due to the controlled release of iodine for wound disinfection or the treatment of iodine deficiency (hypothyroidism), for example, through patches. It should be emphasized that zeolites are easily incorporated into other commonly used materials such as silicones or polymers; therefore, any material requiring asepsis would be suitable for incorporating the new zeolites, such as catheters, etc.

[0019] Examples in the literature of solid materials capable of accommodating high quantities of triiodide and allowing the controlled release of these polyanions are very scarce, as we have already seen above. Furthermore, a key difference between the synthesis procedure for triiodide anions within zeolites that is the subject of this patent and the procedures described in any of the documents mentioned above is that the latter do not use an alkyl iodide as a starting material, nor can they utilize the associated technical effect for obtaining gaseous byproducts (alkene and water), which can be recovered in this patent.The provision of a process for the preparation of triiodide ions within zeolites, an alternative to those existing in the prior art, with higher yield, scalability, and no waste generation, by using an alkyl iodide as an iodine source, which, in contact with the zeolite, gives rise to a cascade reaction of dehydroiodination and subsequent in situ oxidation, generating triiodide ions that are adsorbed onto the zeolite and releasing the corresponding gaseous alkene that can regenerate the alkyl iodide, is the basis of the present patent. Although some documents address the technical problem of the reactivity of alkyl halides within these solid structures, none address the synthesis of triiodide anions.

[0020] The solution in this patent represents a qualitative technical leap with respect to what is already known, going beyond what is assumed with the skill and routine practice of an expert in the field.

[0021] Description of the invention

[0022] The present invention relates to a process for the synthesis of triiodide anions inside zeolites in a single reactor, by means of a cascade reaction of dehydroiodination of alkyl iodides and in-situ oxidation with air, such that the zeolite fills its pores with high amounts of triiodide anion and generates a solid material with application as a heterogeneous catalyst, electrolyte for photovoltaic cells or perovskites, and a controlled release agent of triiodide for disinfection of surfaces, water, or skin infections, as well as a supplier of iodine for hypothyroidism.This process comprises at least the following steps: a) contacting the zeolite and pure liquid alkyl iodide in the presence of air; b) heating the mixture obtained in step (a); c) releasing the gaseous alkene and water, obtained as gaseous by-products in step (b); d) recovering the solid product from step (c); and e) regenerating the alkyl iodide by iodination of the alkene recovered in step (d).

[0023] Alkyl iodides that can be used as starting material must be liquid or liquefiable at the reaction temperature of the system and are described by the general formula (I). At least one of the substituent groups must be a hydrogen atom for the dehydroiodination reaction to occur and the gaseous alkene to be generated. Therefore, the molecular weight of the iodoalkane will normally be between 150 and 300 Da so that it is liquid at the reaction temperature and the resulting alkene is volatile.

[0024] The general formula (I) of alkyl iodides that can be used as starting materials to generate triiodides in zeolite is provided below. Mixtures of compound iodinated vapors can be included in the same synthesis as step (a):

[0025] Where R1-R4 are alkyls (from 1 to 20 carbon atoms, preferably from 1 to 6 carbon atoms) or H, at least one of the groups must be H for the deiodination reaction to occur and the gaseous alkene to be generated, more particularly, at least R 1 It must be H and at least R 2 It must be alkyl. The molecular weight will normally be between 150 and 400 Da so that they are liquids at the reaction temperature and the resulting alkene is volatile. Preferably, mixtures of several iodinated compounds of formula (I) are used in the same synthesis as step (a).

[0026] According to a particular embodiment of the present invention, the zeolite can be of the Faujasite, MFI, LT, halloysite, or any type of zeolite with a network of aluminum and the capacity to adsorb alkane iodides. Amorphous alumina and silico-alumina are also included as usable materials. A zeolite capable of adsorbing alkyl iodides is understood to be a zeolite with a pore size suitable for the access of such molecules, i.e., alkyl iodides. Zeolites with a suitable pore size can be considered to be those with medium pores (approximately 5-6 Å) and those with large pores (approximately 7-8 Å). The pore size of zeolites can be determined using widely known techniques such as the BJH (Barrett-Joyner-Halenda) or BET (Brunauer-Emmett-Teller) methods. According to a particular embodiment, the zeolite has a pore size equal to or greater than 5 Å, equal to or greater than 6 Å, equal to or greater than 7 Å.According to a particular embodiment, the zeolite has a pore size between 5 Å and 8 Å, a pore size between 6 and 8 Å, or a pore size between 7 and 8 Å. Some non-limiting examples of medium-pore-size zeolites are MFI. Some non-limiting examples of large-pore-size zeolites are Faujasite (FAU), BEA, mordenite, or Linde type L (LT).

[0027] According to a particular embodiment of the present invention, the zeolite is selected from the group consisting of Faujasite, MFI, LT type zeolites, and any other type of zeolite with networked aluminum and a pore size between 5 Å and 8 Å.

[0028] According to one particular embodiment of the present invention, the zeolite is of the Faujasite, MFI, or LT type. According to one particular embodiment, the zeolite is of the BEA type. According to another particular embodiment, the zeolite is of the mordenite type.

[0029] According to a preferred embodiment, the zeolite is a large-pore zeolite, preferably selected from faujasite, LT, and BEA, more preferably selected from faujasite and BEA. According to another preferred embodiment, the zeolite is a medium-pore zeolite, preferably MFI.

[0030] According to a further preferred embodiment, the zeolite is of the Faujasite type. According to a further preferred embodiment, the zeolite is selected from the group consisting of Zeolite X (NaX) and Zeolite Y (NaY).

[0031] According to a particular embodiment of the present invention, the Si / Al ratio of the zeolite is between 0 and 99, preferably between 1 and 99, more preferably between 1 and 20.

[0032] According to a particular embodiment of the present invention, the zeolite compensation cation can be any alkaline earth or alkali metal.

[0033] According to a particular embodiment of the present invention, the zeolite can be dehydrated prior to its use in the synthesis. According to a particular embodiment of the present invention, the alkyl iodide of general formula (I), i.e., the alkyl iodide, has that general formula where the radicals R1, R2, R3, R4 are selected from R1-R4 = Alkyls as defined above, or H, and at least the R group 1 It must be H for the deiodination reaction to occur and the gaseous alkene to be generated. According to a particular embodiment, at least R 2 is alkyl, preferably alkyl of 1 to 10 carbon atoms, more preferably of 1 to 5 carbon atoms. In a more preferred embodiment, R 3 and R 4 They are H. The molecular weight will normally be between 150 and 300 Da so that they are liquids at the reaction temperature and the resulting alkene is volatile.

[0034] According to a more particular embodiment of the present invention, the alkyl iodide is selected from the group consisting of propyl iodide, butyl iodide, pentyl iodide, and mixtures thereof. According to a preferred embodiment, the alkyl iodide is butyl iodide.

[0035] According to another particular embodiment of the present invention, the amount of zeolite that the reaction mixture can contain is between 25%-99% by weight, preferably between 50%-90%.

[0036] According to another particular embodiment of the present invention, the amount of alkyl iodide that the reaction mixture can contain is between 10%-99% by weight, preferably between 25%-75%.

[0037] According to another particular embodiment, the concentration of molecular oxygen in the reaction atmosphere will be between 0.1% (1000 ppm) and 100% (pure oxygen) by volume, preferably between 5% and 21% (pure air) by volume.

[0038] According to a particular embodiment of the present invention, the reaction temperature can be between 80 and 300 °C, preferably between 130 and 150 °C. The range is very wide because it depends on the liquid stability of the alkyl halide and the evaporation rate of the resulting alkene; higher temperatures result in a faster reaction rate. According to a particular embodiment of the present invention, the reaction can be carried out under total pressures between 0.01 and 10 bar, preferably at 1 bar (ambient pressure).

[0039] According to a particular embodiment of the present invention, the reaction time can be between 0.5 and 48 hours, preferably between 2 and 18 hours.

[0040] According to another particular embodiment of the present invention, the final amount of triiodide that the iodized zeolite can contain is between 1%-50% by weight, preferably between 10%-25%.

[0041] The amount of triiodide in the zeolite was measured by ultraviolet-visible spectrophotometry both in solution, after calibration with povidone-iodine, and in the solid phase, by diffuse reflectance. Figure 2 shows the exclusive presence of triiodide in the NaY and NaX zeolites, with no traces of stored free diiodine, confirming that the self-protection reaction of diiodine with iodide has functioned with complete selectivity within the zeolite. The greater amount of triiodide released in solution (up to three times more) by the zeolites compared to fully dissolved povidone-iodine is also evident. Figure 3 (diffuse reflectance of the NaY zeolite with triiodide) confirms the predominant presence of triiodide in the zeolite, with some amounts of diiodine.

[0042] According to another particular embodiment of the present invention, the alkene and water by-products can be removed as a gas at ambient pressure or under vacuum.

[0043] According to another particular embodiment of the present invention, the alkene and water by-products can be recovered as gas or liquids after cooling following the reaction.

[0044] According to another particular embodiment of the present invention, the alkene byproduct can be recycled to alkyl iodide by reaction with hydroiodic acid.

[0045] According to another particular embodiment of the present invention, the resulting triiodide-containing zeolite is especially stable against disintegration in hydrofluoric acid. Thus, the product is triiodide stored in the channels of the zeolite, which remains stable for months without any special storage precautions.

[0046] Brief description of the figures

[0047] Figure 1: Synthesis of the zeolite with triiodide described in the present patent of invention.

[0048] Figure 2: Ultraviolet-visible spectra of Na-Beta and Na-mordenite zeolites with triiodide.

[0049] Ultraviolet-visible spectra of NaY and NaX zeolites in solution with triiodide after complete release of the triiodide in water by active diffusion (stirring). The spectrum of povidone-iodine is shown for comparison.

[0050] Figure 3: Diffuse reflectance spectrum of NaY zeolite with triiodide.

[0051] Figure 4: Ultraviolet visible spectra in solution with different amounts of povidone-iodine, for calibration, taking into account that it contains 1% free iodine.

[0052] Figure 5: Diffuse reflectance spectrum of NaY zeolite with triiodide before and after releasing all its charge in water.

[0053] Throughout the description and claims, the word "comprises" and its variants are not intended to exclude other technical features, additives, components, or steps. For those skilled in the art, other objects, advantages, and features of the invention will become apparent partly from the description and partly from the practice of the invention.

[0054] EXAMPLES

[0055] The following are non-limiting examples of the present invention:

[0056] Example 1: Synthesis procedure for NaX, NaY, or HBeta zeolites with triiodide. In a round-bottom glass flask fitted with a magnetic stir bar, 2 grams of commercial zeolite and 5 mmol of iodobutane were added. The mixture was placed in an oil bath preheated to 130 °C and allowed to be stirred magnetically until complete conversion (approximately 20 hours) in an open container, monitoring the reaction by gas chromatography. The directly recovered solid contains 25% triiodides in the zeolite. No further purification steps are required, and the triiodinated zeolite can be stored in a container without any special precautions.

[0057] Example 2: Synthesis procedure of Na-Beta or Na-Mordenite zeolites with triiodide.

[0058] First, the selected zeolite (Na-Beta or Na-mordenite) is placed in a pre-dried, oven-baked round-bottom flask and dehydrated at 250 °C under vacuum for 2–4 hours. Once dehydrated, the remaining zeolite (approximately 0.130 mmol) is weighed out, and 0.5 equivalents of 1-iodobutane (relative to the sodium present in the structure) are added, along with a magnetic stirrer. The zeolite is then placed in a silicone bath at 130 °C and allowed to react for 4–5 hours. After this time, the zeolite has acquired a brown color, indicative of the presence of triiodide. To confirm the presence of triiodide, the zeolite is analyzed using UV-Vis and UV-Vis DR spectroscopy.

[0059] Example 3: Synthesis procedure for non-commercial zeolites with triiodide and with other charge compensation cations other than H + or Na + .

[0060] The procedure described in the example was followed after treating the NaX or NaY zeolites as follows: a 0.1 M aqueous solution of KOAc or CsOAc was mixed with the zeolite (typically 1 gram of zeolite per 10–20 mL) in a round-bottom glass flask fitted with a magnetic stir bar, and the mixture was magnetically stirred in a preheated 70 °C bath for 24 h. After this time, the resulting zeolite was filtered and washed with plenty of water at room temperature, and then oven-dried for 20 h to give the corresponding triiodized KY, KX, and CsX zeolites. In the case of Li, the NaY zeolite was treated with an aqueous solution of LiNCh at 60 °C to give the LiY zeolite. Na-Beta zeolite is prepared with a 1M aqueous solution of NaNO₃ at 80°C starting from H-Beta zeolite, and the zeolite follows the same protocol but with KOAc. In general, the first exchange typically yields 65% L! + or K + exchanged, and 25% of Cs +Therefore, they are repeated once or twice more, ultimately resulting in a typical 75% and 36% exchange percentage for Li. + / K + and Cs + , respectively, in the different zeolites.

[0061] Example 4: Procedure for reusing the alkene by-product.

[0062] Following a typical triiodide zeolite preparation procedure, the resulting gaseous alkene is collected in a gas bag and analyzed by gas chromatography-mass spectrometry to confirm its purity. Variable amounts of alkane may be present, which are not detrimental to alkene recycling or can even be recycled by radical iodination. The resulting alkene is treated with hydroiodic acid to obtain the starting iodoalkane.

[0063] Example 5: Catalysis with triiodinated NaX zeolite.

[0064] 100 mg of NaX zeolite containing 25% triiodide by weight is placed in a round-bottom glass flask equipped with a magnetic stir bar, and excess 1-hexyne is added as a reagent. The mixture is placed in an oil bath preheated to 130 °C and allowed to be stirred magnetically, monitoring the reaction by gas chromatography-mass spectrometry. The progressive transformation of the alkyne to the corresponding ketone in the internal position (Markovnikov hydration) is observed due to the catalytic action of the triiodide. This reaction demonstrates the potential activity of zeolite as a solid catalyst in carbonylation reactions and the reactivity of unsaturated carbon-carbon bonds, which are two typical industrial reactions where the iodine-iodide system acts as a catalyst (Iodine Catalysis in Organic Synthesis, 2022, WILEY-VCH GmbH).

[0065] Example 6: Passive release of triiodide in water with triiodized NaY zeolite.

[0066] 300 mg of NaY zeolite containing 25% triiodide by weight was placed in 100 ml of water, and the amount of iodine released was analyzed over time. The maximum amount of iodine that can be released from the zeolite is 91 mg, which corresponds perfectly with the amount obtained experimentally at the final time (>1000 minutes). Table 1 shows the amount of iodine in the water at different times after its passive release from the zeolite, where a progression in its release is observed. Note that after 10 minutes of the experiment, the amount of iodine is sufficient to purify the water used according to WHO parameters (Wildern. Environm. Med. 2010, 21, 332-336), since the zeolite is much more effective than povidone-iodine. Figure 5 shows the calibration performed with povidone-iodine. Table 1: Analytical results of the passive release of triiodide in water with zeolite

[0067] NaY triiodide.

[0068] Example 7: Active release of triiodide in water with triiodized NaY zeolite.

[0069] The same procedure as in Example 5 was followed, but this time the mixture was vigorously shaken to obtain a quantitative yield of iodine in the water after less than 5 minutes of contact. Figure 6 shows the zeolite after liberation, where it can be seen that practically all that remains inside is diiodine, due to the shift in the triiodide / iodide-diiodine equilibrium to the low concentration of remaining iodides. Example 8: Reluctance of NaX zeolite with triiodide to disintegration in hydrofluoric acid. A known quantity of NaX zeolite with triiodide is added to a fluorinated plastic beaker and covered with concentrated aqueous hydrofluoric acid (large excess), and the mixture is left at room temperature. After a predetermined time, the remaining solid is recovered after dilution with water, vacuum filtration, and drying, to be weighed and analyzed by X-ray diffraction, comparing it with the originally added material.It is observed that NaX zeolite with triiodide is at least ten times more stable to disintegration in hydrofluoric acid than pristine NaX zeolite.

Claims

CLAIMS 1. A process for the synthesis of triiodide anions inside zeolites in a single reactor, by means of a cascade reaction of dehydroiodination of alkyl iodides and in-situ oxidation with air, comprising at least the following steps: a) contacting the zeolite and at least one pure liquid alkyl iodide in the presence of air; b) heating the mixture obtained in step (a); c) releasing the gaseous alkene and water, obtained as gaseous by-products in step (b); d) recovering the solid product from step (c); and e) regenerating the alkyl iodide by iodination of the alkene recovered in step (d).

2. A process for the synthesis of triiodide anions inside zeolites in a single step, according to claim 1, characterized in that the zeolite is selected from Faujasite, MFI, LT, halloysite, and network aluminum zeolites capable of adsorbing alkane iodides, and any combinations thereof.

3. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of claims 1 and 2, characterized in that the Si / Al ratio of the zeolite is between 1 and 99.

4. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the zeolite has a pore size equal to or greater than 6 Å.

5. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the zeolite has a pore size between 6 Å and 8 Å.

6. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the zeolite is selected from the group consisting of faujasite and BEA type zeolites.

7. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the zeolite is of the faujasite type.

8. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the zeolite compensation cation is alkaline earth or alkali.

9. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the zeolite is subjected to a dehydration process prior to its use in step (a).

10. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the liquid alkyl iodide of step (a) is a compound of general formula (I): where: R1, R2, R3 and R4 are independently selected from alkyl, preferably alkyl of 1 to 20 carbon atoms, or H, and where at least R1 must be H and R2 must be alkyl, 11. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the molecular weight of the alkyl iodide is between 150 and 400 Da.

12. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that mixtures of compounds of formula (I) are used in step (a) 13. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the amount of zeolite contained in the reaction mixture of step (a) is between 25%- 99% by weight.

14. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the amount of alkyl iodide contained in the mixture of step (a) is between 10%- 99% by weight.

15. Process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the concentration of molecular oxygen in the reaction atmosphere of step (a) is between 0.1% (1000 ppm) and 100% (pure oxygen) by volume, preferably between 5% and 21% (pure air).

16. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the reaction temperature of step (b) is between 80 and 300 °C.

17. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the reaction of step (b) is carried out under total pressures between 0.01 and 10 bar.

18. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the reaction time of step (b) is between 0.5 and 48 hours.

19. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the iodized zeolite recovered in step (d) is produced in quantities between 1%-50% by total weight of the recovered solid product.

20. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the alkene and water by-products are removed as a gas at ambient pressure or under vacuum.

21. A process for the synthesis of triiodide anions inside zeolites in a single step, according to any of claims 1 to 19, characterized in that the alkene and water by-products of step (b) are recovered as gas or liquids after cooling following the reaction.

22. Process for the synthesis of triiodide anions inside zeolites in a single step, according to any of the preceding claims, characterized in that the alkene by-product is recycled to alkyl iodide by reaction with hydriodic acid in step (e).

23. A process for the synthesis of triiodide anions inside zeolites in a single step, according to claims 1 to 22, characterized in that the triiodide is stored in the channels of the zeolite and is stable for at least 12 months without any special storage precautions.

24. Use of the triiodide zeolite resulting from the process described in any of claims 1 to 22 as a material stable against disintegration in hydrofluoric acid.

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